1. Field of the Invention
This document relates to a touch sensing device and a method for correcting an output thereof.
2. Discussion of the Related Art
Along with the trend of light weight and slim size of home electronic appliances and portable information devices, as a user input means, a button switch is being replaced with a touch sensor.
As the touch sensor, an electrostatic capacitance type, a resistor type, a pressure type, an optical type, an ultrasonic type, etc. are known. A touch screen is comprised of touch sensors formed on a display device.
The touch sensors formed on the display device are connected to a power line and coupled with signal lines of the display device. Due to this, much noise is mixed in outputs of the touch sensors. Further, even when there is no touch input, a large deviation exists between the outputs of the neighboring touch sensors. Such a deviation is referred to as a swing level of touch data. A touch signal processing circuit recognizes a touch when touch data having more than a predetermined threshold value is inputted to a sum of the swing level of the touch data and the noise. The more the noise and swing level of the touch data, the lower the sensitivity of the touch sensors. Particularly, the swing level has a larger effect on the sensitivity of the touch data than the noise has. Therefore, to increase the sensitivity of the touch sensors, the swing level of the touch data should be decreased.
The touch signal processing circuit can compare the previous frame data and the current frame data, and correct touch data according to the result of comparison. However, the cost of the touch signal processing circuit increases because frame memories are required.